In the mid-1950s, Dr. Lyle B. Borst—a physics professor at the University of Utah who had formerly been a reactor designer with the Atomic Energy Commission—and his students in his Physics 280 Nuclear Technology course had a great idea.

Regular locomotives had to make frequent stops to take on coal or oil. How much better would be a locomotive that could travel around the world twice without refueling? This thinking resulted in the X-12, a nuclear-powered locomotive developed by Borst and his students—in collaboration with the Association of American Railroads and several industries, including GM, Commonwealth Edison, Trane, GE and Westinghouse.

The result were patents and a 54-page report: An Atomic Locomotive: A Feasibility Study.The X-12 would have weighed 360 tons and been 160 feet long—so long that the engine had to be divided into two sections, with a flexible vestibule connecting them. The nuclear power source would have been a solution of fissionable U-235, contained in a tank 3 feet long and a foot in diameter. This would, in turn, have been enclosed within a 200-ton shield. Steam produced by the reactor would power turbines which would drive four generators. These would create the 7000 hp of electricity required to power the motors driving the wheels. The entire 65-foot rear section of the engine would have been taken up by the condensers and radiators (equivalent to "1000 automobile radiators").

The X-12 would be so powerful that it would be able to accelerate a 5000-ton train from a standing start to 60 mph in just 3 minutes and 32 seconds.

Borst figured it would cost about $1.2 million to build the X-12...about twice the cost of a comparable four-unit Diesel locomotive. Believing that U-235 could be obtained for about $9000 a pound, and run for a full year between refuelings, Borst thought that his locomotive would be able to "compete successfully with diesel power under favorable circumstances."